In a process of fabricating a semiconductor device or a flat panel display (FPD), a process for performing liquid-treatment by supplying a processing liquid to a target substrate, such as a semiconductor wafer or a glass substrate, has been widely used. For example, such a process may include a cleaning treatment for removing fine particles or contaminants adhered to a substrate.
As a cleaning apparatus for performing such a cleaning treatment, there has been known a single wafer type cleaning apparatus in which while a substrate (such as a semiconductor wafer) is held by a spin chuck and is rotated, the treatment is performed by discharging a chemical liquid from a nozzle to the surface of the substrate to form a liquid film on the surface of the substrate. After the cleaning treatment with the chemical liquid, while the substrate is rotated, a rinsing treatment is performed by supplying deionized water, as a rinsing liquid, to the surface of the substrate, followed by a drying treatment. The drying treatment is performed by shaking off the remaining rinsing liquid through high-speed rotation of the substrate without the supply of any liquid. In order to avoid remnants, such as watermarks, prior to the shaking-off drying treatment, a solvent having a low boiling point and a low surface tension, such as isopropyl alcohol (IPA), is supplied, as a drying solvent, to the substrate. For example, see Japanese Laid-Open Patent Publication No. HEI 10-303173.
However, in such a kind of cleaning apparatus, since a liquid is shaken off from the substrate, a drain cup is provided around the substrate to receive the shaken-off liquid, and a drain tube connected to the bottom portion of the drain cup is provided to discharge the liquid to the outside of the apparatus. The drain cup receives all of a chemical liquid for cleaning, a rinsing liquid (such as deionized water), and a drying solvent (such as IPA) and discharges them to the drain tube.
In general, after the drying treatment is performed by using a drying solvent, such as IPA, a chemical liquid treatment on the subsequent substrate is performed without a rinsing treatment. This causes IPA and the like to remain in the drain cup or the drain tube. In this state, when the chemical liquid treatment on the subsequent substrate is performed, the draining liquid of the chemical liquid is mixed with IPA and the like. Since many chemical liquids used for the cleaning treatment are expensive, the chemical liquids have been recently required to be collected and reused. However, since the above mentioned chemical liquid mixed with IPA and the like cannot be reused, it is wasted. When the chemical liquid is wasted, a waste liquid disposal apparatus is used. Thus, the waste, instead of reuse, of such a chemical liquid causes overload of the waste liquid disposal apparatus.